Anyone had this experience with NXT-G?

This past week, before our FLL competition, one of our FLL teams had a number of errors saving My Blocks.

At this weekend's competition, we experienced having a robot ignore the simplest of programs---rotate motor C 100 degrees. Instead, motors B and C both rotated forward 100 degrees, randomly. We coaches assumed the student had picked the wrong program; but after repeated demonstrations on the practice mat (between rounds) we were convinced that the error was not hers. (sometimes it worked correctly, other times it didn't.

Some NXT "experts" have never experienced these problems, but I'm hearing from others that some teachers have been reporting these errors. I'd appreciate hearing if you have experienced similar problems, so I can get some productive assistance (if it exists).

We are using new Dell laptops (Vista), purchased and managed by a computer professional from our sponsoring company. The software was a group license of NXT-G, purchased from LEGO Education in September 2008. (We own multiple copies, but used one on all of the computers.) Also, there were two teams using the same equipment. The other team did not have the same problem, but, of course, wrote different programs. (They used three My Blocks, while my team used seven My Blocks.)